KR20010033102A - Techniques for etching a transition metal-containing layer - Google Patents

Abstract

A method of etching a transition metal-containing layer disposed on a substrate is disclosed. The transition metal containing layer is disposed under the etching mask. The method includes providing a plasma processing system having a plasma processing chamber and configuring the plasma processing chamber to etch the transition metal containing layer. The plasma processing chamber configuration process includes configuring a plasma processing chamber to receive a source gas including HCl and Ar and constructing a power source in combination with the plasma processing chamber to supply energy to strike a plasma from the source gas. The plasma processing chamber construction process further includes configuring the plasma processing chamber to etch the transition metal containing layer into the plasma.

Description

Etching method of transition metal-containing layer {TECHNIQUES FOR ETCHING A TRANSITION METAL-CONTAINING LAYER}

The present invention relates to the manufacture of electronic devices. In particular, the present invention relates to an improved method of etching a transition metal-containing layer during electronic device manufacturing.

Transition metal containing layers may be used in the manufacture of electronic devices such as computer disk drive read / write heads, integrated circuits, and flat panel displays. The transition metal-containing layer includes one or more transition metals or alloys thereof. Generally transition metals include iron, platinum, cobalt, nickel and copper, as well as metals of the Group IIIA and IIB Periodic Tables. One example of a transition metal-containing alloy is permalloy, an iron / nickel / cobalt alloy used to make thin read / write film heads.

The traditional method of etching the aluminum metal layer is not suitable for etching the transition metal containing layer, so the use of the transition metal containing layer provides a great deal of motivation for the process engineer. For example, since Cl ₂ provides a fast etching speed, etching of the aluminum layer is usually performed using Cl ₂ . However, transition metal chlorides, such as nickel chloride and platinum chloride, are relatively nonvolatile and tend to reprecipitate on the substrate surface during etching, which is fatal to the etching profile and the etching uniformity. For example, the presence of transition metal chlorides on the substrate surface leaves undesired residues, making it difficult to remove masking after etching and poor device performance (eg, electrical shorts due to bridging).

1 illustrates a layer stack 100 showing an exemplary layer stack including a transition metal containing layer. Although only a few layer stacks 100 are shown, there may be other additional layers above, below, or between the layers shown. Thus, although the layers are shown as being in direct contact with each other, they may be separated by one or more other layers in a given layer stack and the terms such as "up" or "down" used do not necessarily require direct contact between layers.

In FIG. 1, the layer stack 100 includes a base layer 102, which may represent a layer or structure underlying the transition metal containing layer. The exact composition and structure of the base layer 102 depends on the electronic device to be manufactured and may be, for example, the substrate itself (eg, silicon wafer or glass panel). The transition metal containing layer 104 is shown on the base layer 102.

The transition metal containing layer 104 may comprise one or more transition metals or alloys thereof, as mentioned. In order to promote etching, a photoresist layer 106 is disposed over the transition metal containing layer 104 to form a mask. The photoresist layer 106 is patterned to form holes 108 and 110 that allow a transition metal etch agent to enter and etch a trench or path in the transition metal containing layer 104.

Etching of the transition metal-containing layer in the known art can be carried out using a sputtering process using, for example, argon as the bomber. Sputtering can bring satisfactory etching speed through the transition metal containing layer 104 if properly controlled as a physical etching process. However, it has been found that the sputtered transition metal is reprecipitated on the substrate surface including the photoresist layer 106, making subsequent photoresist removal steps difficult. In addition, pure physical etching processes tend to have low selectivity for photoresists. That is, the protection region in the photoresist layer 106 may be damaged. Photoresist damage is particularly problematic in modern high density electronics fabrication because these devices are packed closely together and require a relatively thin photoresist layer 106 during fabrication. The compact size and high aspect ratio in these modern high density devices also reduces the sputtering efficiency due to charging.

Another known process for etching the transition metal containing layer 104 uses Ar / Cl ₂ in a high pressure / low density plasma etching chamber, such as a plasma etching chamber, in particular a diode based etching chamber. High pressure processing chamber refers to a processing chamber having an operating pressure of 100 mTorr or more. Cl ₂ is chosen because it provides ions to convert to metal chlorides. Etching speed is mainly controlled by low sputtering efficiency in high pressure / low density plasma reactors. The chlorine reactive species combine with the sputtered transition metal to form a transition metal chloride that is water soluble. Rinsing in deionized water after etching tends to remove most of the transition metal chlorides.

However, even Ar / Cl ₂ has been found to produce unsatisfactory transition metal etch rates when used in high pressure / low density plasma processing chambers. In addition Ar / Cl ₂ has low selectivity for photoresist. This low selectivity for photoresists in the manufacture of modern high density electronic devices makes them unsuitable for using Ar / Cl ₂ of the prior art as transition metal-containing layer etchants in electronic device manufacturing. Thus, due to this low photoresist selectivity problem, many manufacturers have to use hard masks.

In view of the above, there is a need for an improved technique for etching transition metal-containing layers. This technique improves the transition metal-containing layer etch rate while increasing the selectivity for photoresist so that the transition metal-containing layer can be used in modern high density electronic devices.

Summary of the Invention

The present invention relates to a method of at least partially etching a transition metal-containing layer disposed on a substrate. The transition metal-containing layer is disposed under an etching mask such as a photoresist mask or a hard mask. The method includes providing a plasma processing system having a plasma processing chamber and configuring the plasma processing chamber to etch the transition metal containing layer. Plasma processing chamber configuration process configures the plasma processing chamber to receive source gas including HCl and Ar, and plasma processing chamber to supply high frequency (RF) power or RF or other forms of energy to strike the plasma from the source gas. Configuring another power source (eg, microwave) in combination with the < RTI ID = 0.0 > The plasma processing chamber construction process further includes configuring the plasma processing chamber to at least partially etch the transition metal containing layer into the plasma.

In another embodiment the invention relates to a method of etching a transition metal-containing layer disposed on a substrate in a plasma processing chamber. The transition metal containing layer is disposed under the photoresist mask. The method includes flowing a source gas comprising HCl and Ar into a plasma processing chamber and struck the plasma exiting the source gas in the plasma processing chamber. The plasma transition metal-containing layer also includes at least partially etching.

In another embodiment, the present invention relates to a method of etching a transition metal-containing layer disposed on a substrate in a high density plasma processing chamber, wherein the transition metal-containing layer is disposed under a photoresist mask. The method includes flowing a source gas consisting of HCl and Ar into a plasma processing chamber. And supplying high frequency (RF) or other form of energy to at least one electrode of the plasma processing chamber to strike the plasma exiting the source gas in the plasma processing chamber. The plasma also includes at least partially etching the transition metal containing layer.

1 shows a layer stack comprising a transition metal containing layer.

Figure 2 shows briefly the low pressure, high density plasma processing system (inductive pair plasma processing system) used to etch a transition metal containing layer in accordance with the present invention.

3A and 3B show hydrogen optical emission spectra before and after nicket etching.

4 shows the steps used to etch a transition metal containing layer on a substrate.

* Code Description

100 Floors Stack 102 Base Floor

104 Transition Metal Containing Layer 106 Photoresist Layer

108,110 holes 200 plasma processing system

202 plasma processing chamber 204 electrodes

206 High Frequency Generator 208 Tuning Network

210 Showerhead 212 RF Induced Plasma Region

214 Temperament 216 Chuck

218 high frequency generator 220 tuning network

222 outlet

According to one embodiment of the present invention there is provided an improved method for etching a transition metal-containing layer using HCl / Ar as a transition metal etch agent. Unlike the known transition metal etching process using Cl ₂ as the chlorine containing source gas, the present invention reduces the etching mask corrosion by reducing the density of chlorine species present during etching using HCl as the chlorine containing etching agent. Such use, for example, reduces photoresist corrosion and increases selectivity to photoresist.

Each HCl molecule provides one hydrogen atom per chlorine atom during etching. Although the exact mechanism is unknown, it is believed that hydrogen plays a role during the etch of the transition metal containing layer, and that hydrogen increases the selectivity to the photoresist and increases the etch rate of the transition metal containing layer. Further explanation of this recognition will be made in various spectral curves of the plasma during transition metal etching.

In another embodiment of the present invention, the improved transition metal etching method uses an HCl / Ar composition in a high density, low pressure plasma processing system. In general, high density refers to an ion density of 1e ¹³ or more, and low pressure refers to a pressure of less than 100 mT. For example, the present invention uses an inductive pair plasma processing system (TCP brand induction plasma processing system such as TCP ^™ 9600, LAM Research Corp. Fremont, California) during the transition metal-containing layer etching. However, other high density low pressure plasma processing systems such as electron cyclotron resonance (ECR) reactors, Helicon Wave (AMAT), MORI (PMT-Tricon) and microwaves can also be used. After etching, the etched substrate is rinsed using an appropriate rinse solution (eg, deionized water) to remove soluble transition metal chlorides.

FIG. 2 shows a low pressure, high density plasma processing system (induction pair plasma processing system) used to etch a transition metal containing layer using the HCl / Ar composition in the present invention. In FIG. 2, the plasma processing system 200 includes a plasma processing chamber 202. Above the chamber 202 is an electrode 204, shown as a coil in FIG. 2. However, other devices for supplying RF energy to the plasma in the plasma processing chamber may be used. Electrode 204 is excited by high frequency (RF) generator 206 via tuning network 208. In Figure 2 RF generator 206 is an RF energy source at 13.56 MHz frequency. However, other suitable frequencies may be used.

Within the plasma processing chamber 202 is a showerhead 210, which is a gas distribution device for releasing a gas etch material into the RF induced plasma region 212 between the showerhead and the substrate. However, other gas distribution devices such as gas distribution rings or ports disposed on the chamber walls may be used. A substrate 214 with a transition metal-containing layer disposed thereon is introduced into the plasma processing chamber 202 and acts as a second electrode on a chuck 216 that is biased by the high frequency generator 218 via the tuning network 220. Is placed. Like the RF generator 206, the RF generator 218 is also an RF energy source with a frequency of 13.56 MHz. However, other suitable frequencies may be used, including different frequencies from the RF generator 206.

A heat exchange gas, such as helium, is introduced into the area between the chuck 216 and the substrate 214 under pressure (2-10 Torr) to regulate the heat exchange between the substrate and the chuck to ensure a uniform and reproducible etching result. Source gas flows through the showerhead 210 and is combusted by the RF generators 206 and 218 to facilitate etching. The pressure in the chamber 202 is kept low at 0.5-500 mTorr during etch of the transition metal-containing layer. A portion of the etch byproduct gas is exhausted out of chamber 202 through outlet 222 (eg using a turbo pump).

After etching, the substrate 214 is removed from the plasma processing chamber 202 and rinsed in a suitable rinsing apparatus to remove substrate transition metal chlorides formed during etching. Hemgum subsequent process in the TCP 9600 SE ^TM system is performed in one module, the air passivation module (APM) of the TCP ^TM 9600 etching system.

The present invention uses a source gas containing HCl and Ar to etch the transition metal containing layer. The use of HCl instead of Cl ₂ as the primary chlorine-containing etching agent component gas reduces corrosion of the etching mask (ie photoresist mask or hard mask) and increases selectivity to masking materials such as photoresist.

The presence of hydrogen species is thought to contribute to the etching process. The presence of hydrogen is believed to contribute to the high transition metal etch rate and high selectivity to the photoresist. Hydrogen increases the selectivity to the photoresist by passivating the carbon-hydrogen bonds of the photoresist.

To illustrate the role of hydrogen, FIGS. 3A and 3B show optical emission spectra during and after etching of the nickel containing layer. The layer to be etched in FIGS. 3A and 3B is a three-layer structure in which nickel is disposed over germanium and tungsten is disposed thereon. The tungsten layer is about 2500 angstroms thick, the nickel layer is 350 angstroms thick, and the germanium layer is 400 angstroms thick. The thickness of the photoresist layer is about 10,000 angstroms. The three-layer structure of Figures 3A and 3B is disposed on a 4 inch GaAs substrate.

There is no hydrogen peak during nickel etching in FIG. 3A. The associated hydrogen peak is about 656.285 nm (Spectral Library of Persistent Emission Lines, D. S. Malchow, ed. E. G. & G. Princeton Applied Research Co., 1990). Hydrogen peaks are present in the optical emission spectrum of FIG. 3B after nicket etching. 3A and 3B show that hydrogen plays a role in the etching of the transition metal containing layer even though the exact mechanism is not completely known.

Even if the base composition includes HCl and Ar, additives for supplying argon, chlorine and hydrogen to etch the transition metal-containing layer are possible so long as they do not significantly change the basic properties of the etchant. For example Cl ₂ may be added as an etchant which increases the number of chlorine species in the plasma region during etching. Increasing the number of chlorine species may increase the byproduct conversion rate (ie, more sputtered transition metals have been converted to transition metal chlorides). However, since chlorine tends to attack the photoresist, it is desirable to control the amount of chlorine species present so as not to adversely affect the selectivity to the photoresist. By reducing the Cl ₂ or HCl flow rate, one or more inert substances (He, Ne, Xe) can be added. HBr, HI, NH ₃ , H ₂ , H ₂ O, H ₂ O ₂ , CH ₄ , C Hydrogen-containing substances such as ₂ H ₆ , C ₂ H ₄ , C ₂ H ₂ , C _X H _{X + 4} , C _X H _{X + 2} , and SiH ₄ may be added, additionally SiCl ₄ , CCl ₄ , CHCl Chlorine-containing substances such as ₃ , Cl ₂ , CH ₂ Cl ₂ , CHCl ₃ can be added.

In this example, a three layer sandwich structure of tungsten, nickel and germanium on a 4 inch gallium arsenide substrate is etched in a TCP ^™ 9600 SE plasma processing system.

In this example a three layer sandwich structure is etched using a process that includes an HCl flow rate of 10 sccm (standard cubic centimeters per minute) and an Ar flow rate of 50 sccm. The pressure in the plasma processing chamber is about 5 mTorr and the cooling helium pressure is 2 T. The electrode temperature is about 40 ° C. The upper electrode power is set to about 250 watts, like that of the lower electrode.

However, for the same or different substrates the pressure can vary from 0.5 to 500 mT, in particular from 1 to 100 mT. Similarly, the Ar flow rate is about 83% of the total flow rate but the Ar flow rate can vary from 1 to 99%, in particular from 5 to 95%. The exact Ar: HCl ratio depends on the transition metal removal (using Ar as bomber), chloride conversion rate (affected by the density of chlorine species in the chamber), and photoresist corrosion rate. Higher Ar: HCl ratios increase sputtering removal, but the reduced Cl species density tends to lower chloride conversion rates. Conversely, lower Ar: HCl ratios tend to increase chloride conversion rates due to the increased density of Cl species despite the risk of attacking the photoresist. The exact Ar: HCl ratio depends on the etching results required and the configuration of the etching chamber. The exact parameters required for etching will depend on the required yield, etching speed, selectivity for photoresist, composition of the layer to be etched, substrate size, design or parameters of the plasma treatment system.

After etching, the substrate is washed with deionized water in an atmospheric passivation module (APM) of the TCP 9600 plasma treatment system. The washing is carried out using deionized water at room temperature to 90 ° C. If necessary, the substrate may be washed for 30 to 120 minutes.

4 shows the steps used to etch a transition metal-containing layer on a substrate. In step 402, a substrate on which a transition metal-containing layer to be etched is disposed is placed in a plasma etching chamber. The transition metal-containing layer is generally disposed under the photoresist mask to facilitate etching. In step 404 at least a portion of the transition metal containing layer of the substrate is etched using a source gas comprising HCl and Ar in a plasma etching chamber. Some of the etchant by-products, including transition metal chlorides, are discharged from the plasma etch chamber during step 404.

After etching of step 404, in step 406 the substrate is rinsed with water (eg, deionized water) to remove transition metal chlorides from the substrate surface. The temperature of the water used to optimize chloride removal can be varied. In general, increasing the temperature of deionized water improves chloride dissolution and removal rates. In step 408, a traditional post-processing step is performed to complete the manufacture of the required electronic device. Substrates, for example, are further processed to form integrated circuits, flat panel displays, and read / write heads included in many electronic systems such as computers.

The present invention advantageously uses a source gas comprising HCl and Ar for etching the transition metal containing layer. The present invention uses HCl instead of Cl ₂ as the main chlorine containing gas to provide chlorine species for converting metals to metal chlorides. Lower density chlorine species were thought to reduce metal chloride conversion and subsequent removal, so the use of HCl instead of Cl ₂ as the main chlorine source gas is unpredictable. Nevertheless, the reduced density of chlorine species due to the use of HCl source gas improves photoresist selectivity, making it more suitable for use in the manufacture of modern high density electronics.

In addition, HCl supplies hydrogen species to the plasma etching environment. Hydrogen species increase the photoresist selectivity and the corrosion rate of the transition metal-containing layer. In addition, the use of high density (e.g., le ¹³ ion density) and low pressure plasma etching chambers for etching transition metal-containing layers is a transition relative to the etch rate achieved in high pressure / low density plasma etching chambers (used in known transition metal etching techniques). Increase the metal etch rate.

Claims (23)

CLAIMS 1. A method of at least partially etching a transition metal-containing layer disposed over a substrate and under an etching mask, comprising: providing a plasma processing system having a plasma processing chamber; Configuring the plasma processing chamber to etch a transition metal containing layer, wherein the configuring step is configured to receive a source gas comprising HCl and Ar; Construct a power source in combination with the plasma processing chamber to supply energy to strike the plasma exiting the source gas; And wherein said plasma comprises configuring said plasma processing chamber to at least partially etch said transition metal containing layer. The etching method according to claim 1, wherein the power source is a high frequency (RF) power source and the energy is high frequency (RF) energy. The etching method according to claim 1, wherein the plasma processing chamber is a high density plasma processing chamber. The etching method according to claim 1, wherein the source gas is composed of HCl and Ar. The rinsing module of claim 1, further comprising a rinsing module configured to rinse the substrate with water and to configure the rinsing module to rinse the substrate after the substrate is etched with the source gas in the plasma processing chamber. Etching method further comprising a step. The etching method according to claim 1, wherein the metal-containing layer includes a transition metal selected from elements of Group IIIA to Group IIB of the periodic table. The etching method according to claim 1, wherein the transition metal-containing layer comprises a transition metal selected from iron, platinum, cobalt or nickel. The etching method according to claim 7, wherein the plasma processing chamber is an inductively connected high density plasma processing chamber. The etching method according to claim 8, wherein the flow rate ratio of the HCl to Ar is from 1:99 to 99: 1. A method of etching a transition metal-containing layer disposed over a substrate and under an etching mask in a plasma processing chamber, Flowing a source gas comprising HCl and Ar into a plasma processing chamber; Smashing the plasma exiting the source gas in the plasma processing chamber; Etching the transition metal-containing layer into the plasma. The etching method according to claim 10, wherein the transition metal-containing layer comprises a transition metal selected from elements of Group IIIA to Group IIB of the periodic table. The etching method according to claim 10, wherein the transition metal-containing layer comprises a transition metal selected from iron, platinum, cobalt or nickel. The etching method according to claim 12, wherein the plasma processing chamber is a high density plasma processing chamber. The etching method according to claim 13, wherein the plasma processing chamber is an inductively connected plasma processing chamber. The etching method according to claim 14, wherein the source gas is composed of Ar and HCl. The etching method of claim 15, further comprising rinsing the substrate with deionized water to remove the transition metal chloride after etching. The etching method according to claim 12, wherein the flow rate ratio of HCl to Ar is 95: 5 to 5:95. A method of etching a transition metal-containing layer disposed over a substrate and under an etching mask in a high density plasma processing chamber, the method comprising: Flowing a source gas comprising HCl and Ar into a plasma processing chamber; Supplying high frequency (RF) energy to at least one electrode of the plasma processing chamber to strike the plasma from the source gas in the plasma processing chamber; Etching the transition metal-containing layer into the plasma. The etching method according to claim 18, wherein the transition metal-containing layer comprises a transition metal selected from elements of Group IIIA to Group IIB of the periodic table. The etching method according to claim 18, wherein the transition metal-containing layer comprises a transition metal selected from iron, platinum, cobalt or nickel. 21. The method of claim 20, wherein said plasma processing chamber is an inductively coupled plasma processing chamber and said electrode is a coil. 22. The method of claim 21, further comprising rinsing the substrate with deionized water to remove the transition metal chloride after etching. The etching method according to claim 21, wherein the flow rate ratio of HCl to Ar is 90:10 to 10:90.